Research On Low Voltage Ride Through Control Strategy Of Wind Energy Conversion System

The rapid development of wind power generation has brought the possibility to solve the energy crisis and environmental pollution problems.However,a large number of distributed wind turbines connected to the power grid will challenge the stability of the power grid.Therefore,the grid puts forward the requirements for the access of wind turbines.Among them,low voltage ride through(LVRT)capability is an vital index.The fault drop of grid voltage will cause the fluctuation of DC bus voltage,which may damage the converter in serious cases,and even cause the off grid operation of direct-driven permanent magnet synchronous generator(PMSG).Thus,in order to improve the transient characteristics of DC bus voltage and enhance the LVRT capability of PMSG,the voltage outer loop control strategy of grid side converter is improved.Firstly,introduces the background and significance of the topic,and mainly introduces the research status of control strategy of grid-side converter and active disturbance rejection control(ADRC).It shows that the current research hotspots of ADRC are parameter tuning and controller structure improvement.Secondly,establishes the models of each part of the wind energy conversion system based on PMSG,expounds the causes of DC bus voltage fluctuation from the perspective of power balance,and analyzes the decoupling principle and parameter setting principle of double closed-loop PI control.Then,in order to solve the inadaptability of PI controller to nonlinear and strong disturbance wind energy conversion system,linear active disturbance rejection control(LADRC)is adopted.In order to solve the problem of bandwidth parameter tuning of LADRC,BP neural network is introduced,and a bandwidth self-tuning linear active disturbance rejection control based on neural network(LADRC-ST)is proposed.In order to improve the control effect,reduce the bandwidth(cost)of LADRC and not increase the computational burden without changing the controller structure,the known model information of WECS is compensated into the design of LADRC,and a modified linear active disturbance rejection control(MLADRC)applied to wind energy conversion system is proposed.Finally,a 1.5MW wind energy conversion system simulation model is established in Simulink,and the proposed control strategies is applied to the voltage outer loop control of grid side converter.The simulation results show that the transient characteristics of DC bus voltage under the two control strategies are better t han those under PI.